The Best Mistake
by RoseRogers
Summary: It was in that moment when she saw his smile slowly grow into an enormous loud burst of laughter as he tilted his head slightly backwards, clutching his stomach and his eyes clenched tight, that she knew without a doubt that joining Hydra would always be her biggest regret and mistake.


_**The Best Mistake**_

_**It was in that moment when she saw his smile slowly grow into an enormous burst of laughter as he tilted his head slightly backwards, clutching his stomach and his eyes clenched tight, that she knew without a doubt that joining HYDRA would always be her biggest regret.**_

Chapter 1

Katerina Morales. Katerina Savannah Morales. That was her true identity, the girl who had a smile more contagious then anything, the girl who had eyes that she described as a dull dark brown but everyone saw that her eyes were an intimidating black but had this shine of intriguing sparks that made those dull dark brown eyes more beautiful than ever. Katerina Savannah Morales was fun and friendly, she had this charm about her that seemed to make everyone fall at her feet but she never used that as an advantage for selfish uses.

She was caring and strong, she got along with any being, whether an animal or human, she'd probably get along with aliens if it came down to a situation as such. She was able to understand anyone and anything with a mind that was so open to everything. People trusted her and cared for her, and in return she was herself— someone who was always behind you in case you fell backwards and someone who was always in front of you in case you tripped forward. She was a fantastic leader, could've led a whole army of sheep straight into victory with her leadership skills, she made the people around her want to become better people, hell, she could convert a whole prison full of criminals into becoming saints.

She wasn't arrogant but was humble and noble, everyone who knew her, never had anything bad to say about her because no matter how hard they would try to find her flaws they could honestly say that she was the closest damn thing to perfect that ever existed.

But there's no such thing as perfect.

Not even Katerina Morales.

In a world as such, who knows if there was even such thing as good.

Agent Katherine Leslie was someone who was completely convinced that 'good' and 'perfect' was just a fairytale that was too good to be true.

The fact that the 'perfect saint', Katerina, was standing in the HYDRA quarters as Agent Leslie, was pure evidence that she was right. Perfect does not exist.

* * *

Agent Katherine Leslie, to put it in a simple form was an evil, deceiving, cunning little bitch. She was by far one of Hydra's greatest accomplishments, seeing as she was a key to their future plans. Agent Leslie, was physically one of the strongest agents HYDRA had the pleasure of having and had unbreakable mental strength, making her equally as dangerous. For years Hydra had kept Agent Leslie as their own personal upcoming weapon. They had trained her to become as she was, they broke her and fixed her into being unbreakable. They trained her to become adaptable to any situation, meaning that they taught her what pain was, what true pain was and showed her how to strengthen her weaknesses so that no level of pain could hurt her. Hydra had moulded her into being an illusion of perfection.

After four and a half years of intense training, preparation and exhaustion, it was on April 15th, that very day that they had finally prepared her for the serum that they had been inventing for not just years but decades, for that very moment.

Instead of figuring out how to duplicate the super soldier serum, they started fresh. New experiments, new aims, fresh ideas.

After much consulting and planning, they had found and came to a conclusion that they did not want a super soldier, they did not want just damage or destruction, they didn't want someone who could just fight, they needed something stronger than that. They needed to be smart about they're every move.

They needed to change the game.

The game had always been, defeat the enemy, defeat the opponent, destroy the opposition.

But they were prepared and ready to change that.

They wanted something- someone - who would leave scars so deep and so unfixable, something unpredictable and underestimated. They didn't want to just kill the enemy, they wanted to slowly break, and tear the enemy apart, they wanted the enemy to hurt and live through excruciating pain. They wanted they're enemy to remain existent just so that they could stand above them. They wanted their opponent to live in regret and to suffer in their own pain. They're target wasn't just physically aimed, it was mentally aimed.

Hydra was going to slowly torture S.H.I.E.L.D, they were going to break shield so much that even the slightest thought of Hydra would cause disastrous amounts of displeasure, discomfort, pain, and suffering. They were going to find all of S.H.I.E.L.D's weaknesses and flaws and toy around with those imperfections, they were going to reach in and play with their minds, bodies and souls. With what they had installed for S..H.I.E.L.D's future, Hydra was ready to subtly and discreetly stab them in the back with cold hearted grins.

Hydra had the mentality to always be in front of everyone, they wanted to be able to predict time and exterminate potential threats, they wanted power, they wanted to open minds and make the world see that earth was of more worth and power than estimated. They needed global domination and knew exactly how. They were going to tear the old world apart to build a new world.

They had developed a plan. Using a simple serum which would increase, magnify and heighten all human senses. What they had done was not a single process but multiple processes. It was also not an easy process nor a short process. It contained decades of work, experimenting, deaths, risks and almost blowing their cover but it was all worth it.

The first procedure was small and barely painful, but their final procedure after a time span of 4 and a half years was predicted and eventually proved to contain more pain then any human could ever experience, but the previous multiple procedures were building the subject up for that final procedure. Everything that they had worked on would finally prove worth every drop of sweat that had dripped because of this.

This was nothing like the Super Soldier. This was imperfect, dangerous, harmful, cunning damage all disguised with an illusion. This was a deceiving illusion. A small entertaining magic trick.

It was a cold heart disguised with a warm smile, it was complete destruction disguised with Katerina Morales also known as Agent Katherine Leslie.

Hydra was winning a game that SHIELD didn't even know existed.

* * *

_**September 2004**_

Katerina was recruited into Hydra after a complete unpredictable tragedy. Her whole family was assassinated and it was a simple mistake by the assassin that somehow left Katerina alive while the rest of her living bloodline was rotting in their graves. Her father and mother somehow ended up on the wrong side of S.H.I.E.L.D resulting with everything backfiring and her parents becoming known enemies to S.H.I.E.L.D, they had perfected Bruce Banner's unsuccessful experiment and were willing to reveal their findings to S.H.I.E.L.D. For some unknown reason, when they had explained their findings, they were rejected by the agency and were told to shut down everything they had researched or S.H.I.E.L.D would proceed to do so. But Mr. and Mrs. Morales were convinced that they worked too damn hard on their research, which was successful, just to be thrown away. They continued their research and was ready to offer information to the military force about their research but before their presentation took place, they and their family were assassinated. The case was given to S.H.I.E.L.D by the government but seeing as S.H.I.E.L.D were at fault for the assassination, the case was never closed but was rather wiped out from all databases, making sure that the event was practically non existent.

It was one of S.H.I.E.L.D's biggest mistakes.

Alexander Pierce, who was a known and trusted associate of S.H.I.E.L.D and also Patrick Morales' (Katerina's father) oldest friends, was left to take legal custody of her until she was of age to be her own legal guardian. Alexander had been a fatherly figure all of Katerina's life and was her godfather, so it was no surprise that he was her legal guardian.

It was in Alexander's best interest to bring Katerina into his work organization. However it was not S.H.I.E.L.D he wanted Katerina to be involved in, it was Hydra.

Pierce was not loyal to S.H.I.E.L.D at all, he had indeed been on the opposing side all that time he served as a S.H.I.E.L.D associate. Seeing as he was extremely trusted and respected, no one questioned his loyalty towards the organization, not even Nicholas Fury. He was a mole in S.H.I.E.L.D but nobody ever saw it, in fact S.H.I.E.L.D was completely blind, they didn't even know Hydra existed. As far as the organization was concerned, Hydra was destroyed years before and was nothing but a bedtime story.

Seeing as Alexander's true loyalty was with Hydra, he introduced Katerina, to Hydra. He taught her and guided her throughout everything. He spoke as if what Hydra was doing was for the better. He told her that S.H.I.E.L.D was at fault for her parents deaths and it was in Hydra's favor to destroy S.H.I.E.L.D.

Pierce took care of changing her identity, knowing that it was a threat to her because of her relation to her parents.

It was through Alexander Pierce that Katerina Morales became Agent Katherine Leslie.

* * *

_**NOVEMBER 2004**_

When Katerina was first introduced to Hydra as Katherine Leslie, she quickly adapted to the name. At first she was not very quickly liked seeing as she was one of the only female agents and was fresh meat meaning that she had not yet earned anyone's loyalty. But after formally meeting her, everyone seemed to trust her in a heartbeat, it was amusing to Alexander seeing as he had no doubt that she would be able to charm her way into everything. It was one of the reasons he decided to recruit her.

She began training immediately by Agent Brock Rumlow who gave her everything. He was strict and difficult and made sure that she worked to the extreme. She was even put on a strict diet to which she accepted but thought it was a bit overboard. After many sessions with Agent Rumlow, an unspoken friendship started to develop.

'Agent Rumlow' turned to 'Brock' and 'Agent Leslie' turned to 'Katherine' or 'Kath' or 'Kathy' most often 'Kat' at times as an attempt to annoy the girl who always seemed calm, 'Kit Kat'. The first time he called her that was when she accidentally scratched his face leaving a cut that healed in less than a week but it was quite a laugh. They had been practicing hand to hand combat when somehow she was stuck in a position where her 'only' defense was to scratch him. He told her she resembled a cat to which she responded with claw like hands, it was a memory which only they understood.

He knew she hated being called the name which was exactly why he teased he with it. But he stopped calling her that after she called him Brick Dick. They would tease each other and call each other names but it was friendly and amusing to not only them but their other agents. Brock and Katherine slowly started to trust each other. Agent Rumlow was one of Hydra's best Agents, he was a sleeper agent in S.H.I.E.L.D and was flawless in physical combat and was an expert sharpshooter, he had advanced skills of a fully trained soldier, it was obvious as to why he was valued in Hydra.

Out of everything he was most valued for his skills in hand to hand combat, martial arts after having experience in street fighting before joining Hydra. So naturally he taught Katherine what he knew, he was completely strictly and made sure all he kicks, flips, hits, positions, postures were exactly how they should be. He pushed her to extreme limits and then pushed her even further. Eventually along the lines, from what he taught Katherine and from what she taught herself, Katherine was able to take down anyone and anything with her own fist, even against Rumlow himself.

She also started immediately having psychological sessions with Agent Cruz. In these sessions she was constantly tortured and hurt. It was in these sessions where she started to learn just how ruthless her enemies would be. In these sessions she learnt how to deceive, distract, lie, manipulate and most importantly, learnt how to overcome weaknesses. She also learnt in these sessions how to read other people, it was important to use every sense to her best ability meaning she had to listen out for unsteady breathing or look out for subtle twitches or notice injuries or realise what type of person that person was, she needed to be able to find weaknesses quickly, she had to know what her enemy was capable of and had to know the exact weak spot and soon enough she did.

She learnt the importance of her senses. Every word that was said would either hurt her or hurt the enemy, what she had to learn was how to make sure that the only words being said would be hurting the enemy. Every move no matter how big or small, whether it be completely obvious or just the movement of a single nerve, every move counted. She had to learn to control her mind and reactions so that nobody could see what her mind knew. In one of the sessions she was electrocuted every time a single muscle was moved. But in the end she knew it it was all worth it, because by the end no matter how hard anyone tried, even Agent Cruz, herself, couldn't get into Katherine's mind. And that was exactly what they needed.

With that she also started weaponry sessions, she'd learn to adapt to any object whether sharp or blunt, whether it was a gun or a stick. She was guided by Agent Jack Rollins who eventually became just Jack. In these sessions, although it required a lot of physical activity, it required your mental activity much more. This was about adapting to anything meaning you had to be smart. Even the smallest object could save your life and Katherine needed to fixate that into her mind before things got serious. In these sessions she also had to learn every name of each weapon Hydra had, she had to be able to memorize the bullets and which gun they belonged to, she had to pick up on damage caused by each specific weapon, she needed to identify her surroundings at all times.

She had to learn how to shoot perfectly both close range and point blank range. She learnt how to use rifles, machine guns, sniper rifles, grenade launchers, pistols, bladed weapons, shot guns, cross bows, bow and arrows. But with that being said she also learnt how to use every day objects to the best advantage; she learnt how to take down someone with just a pencil. She learnt how to take someone down with a single elastic band. And then she also had to learn how to do the opposite. Because with attacking also comes defending.

She had to learn how to disarm weapons and explosives. With defending she needed to know what resources around her could protect her from what she was up against — whether it be a proper shield or a piece of clothing. She had to know the exact place to throw a grenade, she needed to know the exact timing of when to shoot, she needed to know exactly where to shoot a target based on whether it should injure the target or kill the target, she needed to learn how to steady her breathing from shaking which could cause a major downfall. Soon enough she was able to use anything to her advantage to get what she wanted. Soon enough she was using a range of something as little as a pin to a full explosive tank to take someone down. Soon enough she was even able to take down Agent Jack Rollins with a single pencil while he held a pistol.

* * *

_**JUNE 2009**_

"Kath, there's really no easy way to say this but what is wrong with you today, your defense is all over the place, what's up?" Brock said to Katherine as she tripped after attempting a combat move that usually she was perfect at.

She was going for a takedown which consisted of a combination of hard end kicks and a hopeful flip which in this case was harder then usual, her attack for the takedown didn't work because her posture during the flip just wasn't sharp enough resulting in a complete collapse. She was confused as to why Hydra was seen as abominable, after all if it wasn't for Hydra, Katherine wouldn't be half the woman she was.

Hydra was known as one of the biggest terrorist organizations in history yet all they had done was given her hope for a better future and also gave her reason to fight. She wanted to know the dark side of Hydra that she knew everyone was hiding from her. She wanted to understand what was so bad about this organization that she was a part of, that it was supposed to die along with Baron Von Strucker those many years ago. She didn't understand Hydra. And it was on her mind for longer then just a while.

"I don't know Brock, I'm just kind of got my head all over the place since I woke up, but yeah I don't know." She answered him as he swiftly pulled her up by the arm.

It was then that he noticed how distant she seemed and he knew that something was up.

"What's going on in that head of yours Kat?" He questioned her as her eyebrows furrowed getting lost in thought.

"Brock I'm not stupid." She sighed, he didn't know where this came from and was slightly confused.

"Um, trust me I know you're not, you're one of the brightest people I know." He replied, scratching the back of his head still confused.

"Brock, I've heard the stories. Hydra isn't very... um, I don't know. It's just, I mean, well, Hydra is meant to be like long gone dead. And for a good reason too, I mean the organization is known as a historical, long gone terrorist organization. This organization was practically worse than the Nazi's." She was confused.

"Katherine," Brock started, at the mention of her full name she knew this conversation had just hit serious.

"Hydra has bad history, but right now, we just need to take out S.H.I.E.L.D, we're just trying to build a new and better world." He explained.

"Yeah but at what cost." She pressed.

"S.H.I.E.L.D assassinated your family because your parents were smarter than the whole organization."

"I'm not talking about S.H.I.E.L.D, I'm talking about Hydra. What is Hydra actually doing and if it really isn't so bad, then why are we 'non-existent' while S.H.I.E.L.D remains assassinating people with high intelligence?"

"If a head is cut off-"

"Two more will take it's place."

"Exactly."

"Brock that doesn't even slightly answer my question."

"I don't know." He admitted as he sighed looking at her.

"All I know is that we're taking down S.H.I.E.L.D and that's all I really need to trust whatever this organization has installed for the future."

"You're right, yeah, you're right. We're taking down S.H.I.E.L.D and that's all that matters. Sorry about this I'm just confused a bit lost but you're right." She was lying, but with what she had learnt and observed over the past years, nobody would ever know when she was telling the truth, no matter how hard you tried.

"So we can get back to when I was kicking your ass." Brock joked, convinced that was the end of the conversation.

"Oh shut it Rumlow, you're gonna regret saying that the second your head is in the ground." She replied with a smirk and that famous spark in her eyes.

"Please, your technique is all over the place."

And with that being said she turned round and did the combination combat move that she was previously failing but this time she performed it with utter perfection. Brock was on the ground as she had he foot at his neck and his leg bent and arms wide apart.

"What was that?" She said, smiling triumphantly. They heard someone on the side clapping. They both turned to look at who it was and got up whilst smiling when they saw Alexander.

"Excellent work Kat, with moves like that you'll have all the men at you're feet." He joked.

"Ha ha very funny Al." She scowled as she hugged him.

"Nice to see you Agent Rumlow." Alexander said, shaking the agents hand.

"You too sir."

"Now Kathy, you're coming with me as Rumlow has some business to take care of."

"See you later, Kit Kat." Brock said, with a smirk.

"Don't get yourself killed Brick Dick."

"I will never understand you two." Pierce said to the two of them chuckling softly.

"Me neither, to be quite honest," Katherine replied, as she and Pierce walked off. It was silent as they walked until they got to the room which was isolated and highly guarded with advanced technology.

Alexander stared at a single screen as it scanned his eye then suddenly the doors slid open. This was part of the normal schedule that Katherine was going by. This was yet another procedure of needles and scans and adjustments which once completed then she could continue on with her day as usual. The only difference was that this was her final procedure. This was the last one and after this it was complete. After the last 4 and a half years this is what all those training sessions with Brock, and her psychological sessions with Agent Cruz, and the painful physical and mental torture that had to occur, and the weaponry sessions with Agent Jack Rollins, who she was also good friends with, this final procedure was what everything had been worked for.

To say Katherine Leslie was nervous would be a complete understatement. She was absolutely terrified out of her God damned mind, but she wasn't going to let the last four years of her life go to waste. She was not going to leave her family to die for nothing. This is what was required of her. This would benefit her in ways that seemed impossible. She knew what the serum would do and she was prepared. She reminded herself over and over again that she had no reason to be nervous.

She heard all the scientists and other associates quietly talk about the process. She heard Alexander talk to her but she wasn't quite listening. She was what all agents called 'in the zone'. Agents would focus everything on to a single thought and push their hardest to not lose focus, it was simply just to ignore the things that they did not want to acknowledge. Katherine Leslie was in the zone and nothing would get her out until after the process was finished.

She was led into a lab where there were wires of all sorts and a machine which was made for her. There was a seat which was surprisingly quite comfortable but Katherine knew that comfort wouldn't last long. She turned so that her body was positioned correctly. Scientists hooked wires around her body and she knew just by the look of everything that this was going to be one hell of a procedure. One man pushed a mouth guard in her mouth to suppress the pain. As everyone was preparing for it she saw Alexander who stood by the wall and he gave her a comforting smile and gave her a small thumbs up. She rolled her eyes but was trying to hide the giggles that she wanted to express.

"The procedure will begin in 5..." Someone announced.

This was it.

".._**4**_..."

It's probably too late to get out of this, she thought.

"..**_3_**..."

She clenched the side of the chair, her knuckles turning a pale white.

".._**2**_..."

She clenched her eyes as tight as possible.

"..**_1_**..."

This was it.

An enormous amount of energy flowed right through her, and it hurt like hell. She was starting to question if this was worth it. It better be, she thought. Another burst of energy ran right through her again to her very own bones. She screamed, as she bit into the mouth guard. Her veins were bulging out of her skin, in her neck and arms and everywhere. There was no word that could explain the amount of pain that she was feeling. She screamed louder and Alexander stood watching, regretting his decisions of recruiting her. He couldn't stop it now though, they'd come too far to give up. He watched as her body started to transform.

She already had a great figure but this was simply extending her whole physique. She was one of the strongest agents Hydra had, with this process Alexander could already see how much this would affect her. She was started screaming again but no one made any move to stop, it was the for the best. The jolts kept continuing through her body as the needles began to press into her. This caused even more pain, if that was even possible, to the girl. The girl. The nineteen year old girl. She was the only person who had the capability to go through this.

Everyone else that they had looked into were all crossed off the list the second Hydra saw how valuable Katherine was. She was a master manipulator, an incredible soldier, a flawless sharp shooter, a fantastic fighter, she had charm, fight, determination, leadership skills, she had everything that they required. She was key to the destruction of S.H.I.E.L.D and everyone knew it.

As the procedure came to an end at last, Alexander Pierce knew that every inch of regret he ever had was long gone, because what he had helped create right in front of him was simply something that he could never and will never ever regret.

Agent Katherine Leslie.

The perfect illusion.

As all lights and flashes and sound came to a stop, all eyes were transfixed on the nineteen year old girl who had just suffered more pain than one could imagine. They all waited for her next move. Suddenly all wires were ripped off her as she reached towards her mouth to pull out the mouth guard. Her whole body felt as if it were on fire, she felt numb but at the same time she felt refreshed and complete. She already started to notice the increase in her senses. She could see much clearer and she had a pretty good prediction that she would probably be able to see in the dark, she made a mental note to test that out.

There was a slight ringing in her ears which was slowly starting to drift away and as it did so, she started to hear everything much more clearly. She could hear the whispers being exchanged and the rustling of keys outside the lab, she could hear what was going on in the room next to the lab. She was completely, utterly amazed. She could also feel a certain energy that seemed to run through her veins, her mind was more alert than ever. A strong smell of chemicals and a burnt like smell drifted in the air although she was sure that only she could smell it. She felt strong and more alive than she's felt in a long time.

"How do you feel?" Alexander asked her with a huge grin on his face.

"I don't know how to explain it. There's so many things that I feel right now, Al I didn't think you actually meant it when you said that the process would be worth it in the end but boy was I wrong. How do I feel? I feel fucking amazing." She said to him as his grin slightly faltered at the cuss.

"Katherine what have I told you about that mouth of yours."

"Pierce I think I've earned the right to let off a single swear word don't you think?"

"I agree!" A couple of scientists said to which she thanked them.

"Yeah I guess so." Alexander said his grin back to being as bright as it was. However, Katherine picked up on how deadly his smile looked. Although his smile seemed bright and ecstatic, she saw just how happy he was because his plan of vengeance was finally going to begin. His smile showed pride. No matter how bright and proud that smile of his was, Katherine couldn't shake the sense that it said danger all over it.

And wasn't just because she had all her senses magnified.

It was danger and anyone could see it.

* * *

So this is a new Avengers/Captain America/Steve Rogers story and my vision is to make sure that this story does link up with the plot of The Avengers and also The Winter Soldier but at the same time trying to make this story as original as possible. So yes all rights of the Marvel Characters go to MCU but I will have slight changes and of course original characters that are mine. Anyways please review so I know what you're thinking XX ;)


End file.
